The invention relates to detecting combustor flashback/flame holding using a temperature sensor.
In a gas turbine, fuel is burned with compressed air, produced by a compressor, in one or more combustors having one or more fuel nozzles configured to provide a premixing of fuel and air in a premixing zone located upstream of a burning zone (main combustion zone). A gas-turbine combustor is essentially a device used for mixing large quantities of fuel and air and burning the resulting mixture. Gas-turbines with combustion systems designed to reduce NOx emissions to levels below 40 ppm without water or steam injection employ a combustion process in which fuel is uniformly mixed with air prior to the combustion process. In the premixing zone, ignition of the fuel and air occasionally occurs. This event, regardless of its cause, is called a “flashback.” Due to the design of most premix systems, the combustion of fuel and air in the premix section usually causes considerable damage to components. For various reasons, it is often not practical to design a low NOx combustor to operate satisfactorily with a flame in the premix section.
Previously, flashback/flame holding had been prevented by having a flame holding margin and limiting the type of fuel that can be burned. Catastrophic damage to the fuel nozzles (and potentially any gas turbine hardware downstream) can be avoided by detecting the occurrence of flashback and by quickly taking remedial action. Additionally, with the use of a flashback detecting sensor, fuel flexibility can be enabled so that higher-order hydrocarbon fuels and/or fuels containing a portion of pure hydrogen can be burned.